Apply the consumer surplus formula to your own demand and supply equations. Get consumer surplus, producer surplus, deadweight loss and a shaded diagram, step by step.
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The Consumer & Producer Surplus Calculator turns a linear demand curve and a linear supply curve into a full welfare analysis: the market equilibrium, the shaded surplus regions, and the deadweight loss any price control creates.
Enter demand as P = a - bQ and supply as P = c + dQ, then optionally add a price ceiling or a price floor. The solver crosses the two curves in closed form, applies efficient rationing on both sides of a binding control, and evaluates each welfare region with the trapezoid area formula — which collapses to the familiar triangle whenever the region has a zero right-hand height. Six worked steps show the consumer surplus formula, the producer surplus formula and the deadweight-loss triangle with your own numbers substituted in, and the downloadable diagram shades all three regions over the demand and supply curves.
For a linear demand curve the consumer surplus formula is one half times the quantity traded times the gap between the choke price and the price paid. When a binding price control leaves buyers unsatisfied the region becomes a trapezoid, so the general formula is one half times the traded quantity times the sum of the gaps at the two ends.
Producer surplus is the area between the price sellers receive and the supply curve, out to the traded quantity. With a linear supply curve that is one half times the traded quantity times the sum of the price gaps at zero units and at the traded quantity.
Deadweight loss is the surplus destroyed when a market does not trade the efficient quantity. It is the triangle between the demand and supply curves over the units that go untraded, and it equals free-market total surplus minus the total surplus actually achieved.
A ceiling below the equilibrium price makes buyers want more units than sellers are willing to produce at that price. Quantity demanded exceeds quantity supplied, and the gap between them is the shortage. Only the smaller quantity supplied is actually traded.
Yes. If demand is much less steep than supply, the price cut buyers enjoy on the units still traded can outweigh the surplus lost on the units no longer traded. Total surplus always falls, because a binding control always creates deadweight loss.
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